The present invention relates to a device for transferring electromagnetic waves, and particularly to a directivity enhancement of its field pattern. More particularly, the present invention can be advantageously applied to a vertical polarization antenna by enhancing the front-to-up and down ratio (vertical pattern) thereof.
In the existing communication networks of mobile telephony of the second generation, it is the case that the cellular coverage of an area is formed by the transferring devices of the base station subsystem. Namely, antennas for radio transmission are installed at a same location with the other elements of the communication network. Therein, it is appropriate to mount these antennas such that they do not influence each other, while having a good transmission efficiency to/from a respective counterpart. Actually, the antennas are preferred to be installed on top of each other as, for example, a Location Measurement Unit (LMU) antenna below or above a Base Transceiver Station (BTS) antenna.
As is clear from the above, these antennas installed on top of each other need to be sufficiently isolated so that they do not influence each other. That is, the beam angle of the vertical field pattern should be formed narrow. When referring to FIG. 1(b) showing a prior art field pattern emitted by an antenna 11, it is apparent that this antenna 11 influences any antenna which would be mounted above or below at a too near distance.
There are some measures known to improve the pattern angle such as to increase the numbers of the radiators of the antenna, to provide longer omni monopoles, to combine radiators in phase, to add upper and lower groundplanes (reflectors) with resonator 1/N-wave pin""s at the edge, wherein these upper and lower groundplanes can be also RF-traps by connecting two planes together at close 1/N-wave distance.
However, every of these measures suffers from at least one severe drawback. Namely, most of them lead to an increase in the size of the antenna or are simply very difficult to handle. In addition, some are visually not acceptable.
Therefore, it is an object of the present invention to provide a device for transferring electromagnetic waves which is free from the above drawbacks.
According to the present invention, this object is solved by providing a device for transferring electromagnetic waves, comprising at least one element for transceiving electromagnetic waves, wherein such an element includes a member for transceiving electromagnetic waves and a member for feeding said transceiving member, and both members are electrically connected with each other, and a conductor strip which is bent round each of said transceiving elements so that sources of unwanted radiation pattern along said transceiving elements are covered, said conductor strip having a flat shape so that regarding its cross section, a thickness perpendicular to said transceiving element is small with respect to a dimension of said conductor strip parallel to said transceiving element, the extension of which dimension also suffices to cover said unwanted sources, wherein each of said conductor strips is grounded at both ends to a common electrical point.
With such a structure, the field pattern of the system is improved in a way that the non desired polarization pattern in a direction perpendicular to the plane of the conductor strips becomes negligible.
As advantageous modifications, the distance between said conductor strip and a corresponding source of unwanted radiation can be chosen to be less than half the width of said strip. This is considered to be the maximum effective distance. Regarding a minimum distance, the arrangement should be such that neither the performance nor the device matching is affected by capacitive coupling.
The device for transferring electromagnetic waves may further comprise a grounding element which in case of directional device can act as a reflector with respect to the transceived electromagnetic waves.
In case if several transceiving members are present in the present device, they are combined in phase, and the conductor strips are grounded at both ends by being directly connected to said grounding element.
Instead of a direct connection, the conductor strips may also be coupled to ground, for example capacitively.
In order to take a phase difference between several transceiving elements into account, the conductor strips are preferably electrically connected together through a suitable phase shift according to this phase difference of the transceiving elements.
With respect to the structure of the device for transferring electromagnetic waves, one or more of said transceiving elements can comprise multiple transceiving members and one feeding member electrically connected thereto. Then, the distance between said conductor strip and a corresponding source of unwanted radiation is less than half the width of said strip at each of said sources.
Of course, the device for transferring electromagnetic waves may form an antenna, wherein said transceiving members are dipoles and said multiple transceiving members are multiple dipoles. As examples for antennas in the present field, a vertical polarization antenna or a horizontal polarization antenna are provided.
The device according to the present invention as well as its modifications solve the above stated problem without increasing the size of the device. Further, additional costs will be very low in comparison to the prior art, making the applicability of the present invention high. Moreover, the present invention can easily be applied to already existing and mounted device structures.